13 April 1970: At 10:07:53 p.m. Eastern Standard Time (mission elapsed time 55:54:53), while Apollo 13 and its crew, James A. Lovell, Jr., John L. Swigert and Fred W. Haise, were approximately 200,000 miles (322,000 kilometers) from Earth enroute to a landing at the Fra Mauro Highlands on The Moon, an internal explosion destroyed the Number 2 oxygen tank¹ in the spacecraft’s Service Module. The Number 1 tank was also damaged. Two of three fuel cells that supplied electrical power to the spacecraft failed.
Jack Swigert radioed Mission Control: “I believe we’ve had a problem here.” ²
Mission Control: “This is Houston. Say again, please.”
Jim Lovell: “Houston, we’ve had a problem. Main B Bus undervolt.”
With oxygen supplies depleted and power failing, the lunar landing mission had to be aborted, and the three-man crew evacuated the Command Module and took shelter in the Lunar Module.
This was a life-threatening event.
The story of Apollo 13 and its crew and their journey home is well known. The 1995 Ron Howard/Universal Pictures film, “Apollo 13,” takes some artistic license, but is generally accurate and realistic.
Five years before Apollo 13 was launched, an engineering decision had been made to increase the spacecraft electrical system from 28 volts to 65 volts. This required that every electrical component on the vehicle had to be changed to accommodate the increased power. The after-accident investigation found that the team that designed the cooling fans for the oxygen tanks was never informed of the change.
During the actual flight, the wiring inside the tank heated to approximately 1,000 °F. (538 °C.), and in the pressurized pure oxygen, the insulation caught fire. The tank, originally installed on Apollo 10, had been dropped when it was removed for modification. It was repaired and later used on Apollo 13, however, it had been weakened by the damage. The extreme pressure caused by the heat of the burning electrical wiring in the containment caused the tank to rupture.
¹ Serial number 10024X-TA0009
² The official mission transcript attributes this statement to Jim Lovell, however, in Lovell’s recollection, it was made by Swigert.
© 2017, Bryan R. Swopes
4 thoughts on “13 April 1970, 03:07:53 UTC, T+55:54:53”
I have to give you credit for the great summaries and technical descriptions you provide each day! Always enjoyable reading and informative.
Thank you, Norm. I appreciate your kind words. —Bryan
5 years before liftoff (1965)
The 28v dc system used in flight in the lunar module was changed to accept 65v ac on the ground. The manufacturer failed to pass this requirement to the vendor and continued to use thermostat switches with a 28v capacity. Note: This only presented a problem if the thermostats were abnormally used a long time on the ground, it didn’t cause a hazard in flight as the successful Apollo 7 – 12 missions used these same switches.
2 years before liftoff (1968)
The cryogenic tank was dropped during maintenance of Apollo 10. It fell only a few inches but it had to be removed to repair the damage, another tank went on Apollo 10.
1-2 years before liftoff (1968-69)
The repair of the damaged tank missed a damaged fill tube. The tube was bent restricting the emptying of the tank.
20 days before liftoff (March 1970)
After a practice session ground crews tried to empty the tank and couldn’t because of the tube restriction. After discovering the damaged tube it was determined that the launch would be delayed by over a month if they had to replace the tank. Rather than delay the launch they devised a work-around (it is here that you ask “What were they thinking!!”). Their work-around involved turning the tank heaters on to heat the material causing it to flow through the restricted tube faster. Note: The heaters are normally only turned on for a short period of time but their work-around involved running them continuously for 8 hours.
19-20 days before liftoff (March 1970)
During the 8 hour heating period the 28v flight thermostats were run with 65v ground power. The thermostats were supposed to open the circuit when the temperature reached 80 degrees but the higher voltage fused the contacts so the heaters continued to run during the entire period. It is now estimated that the temperature inside the tank may have reached 1,000 degrees. Sensors inside the tank were supposed to monitor the temperature but because the thermostats were set at 80 degrees the sensors only recorded up to 100 degrees (Murphy was very busy with this one).
Liftoff (April 1970)
Apollo 13 lifted off with the damaged cryogenic tank. Unknown to NASA, the 1,000 degree temperature had melted the insulation from a motor wiring within the tank leaving bare wires.
Liftoff plus 56 hours (April 13, 1970)
When the crew started to fill the tanks with oxygen the bare wires sparked causing a fire and the resulting explosion.
Apollo 13 is a textbook example of human error and of human ingenuity.
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